Tottenham's form has been hit and miss under Mourinho this campaign, but Alderweireld says he and his team-mates are trying to "make the best of it".
Opening up on Mauricio Pochettino's sacking and Mourinho's appointment, Alderweireld told Het Nieuwsblad: "For me it was bad news because you are always loyal to your trainer.
"The next day another trainer suddenly comes to you. That was very strange, but that is also part of football. Then you try to make the best of it."
He added: "Pochettino was fired when I was playing a match with Belgium. I got the news when I got into the dressing room.
"Immediately afterwards I got questions about it from Belgian journalists. It all went so fast that I didn't have time to think about it."